An example of a prior art electromagnetic relay is shown in FIG. 9. Movable component 3 is supported by an upper end of coil block 2 in a way that it is free to rotate; coil block 2 is set on base 1. Movable component 3 comprises movable contact element 4 and movable iron member 5, which are held together and isolated from each other by resin retainer 6. Movable component 3 has several parallel movable contact elements 4, which are formed integrally to retainer 6 by an insert molding process. Movable iron member 5 is securely attached so as to be integral to the same retainer 6.
In the absence of magnetic excitation, the restoring force of spring 7 in FIG. 9 causes coil block 2 of this electromagnetic relay to rotate counterclockwise. Movable contact 4a on the lower end of movable contact element 4 comes in contact with fixed contact 8a on fixed terminal 8, which is pressed into base 1. When a current is applied to coil block 2, the movable iron member 5 is drawn toward core 9, which projects from the end of the coil block 2. Movable component 3 then rotates clockwise, and the movable contact 4a comes in contact with the other fixed contact, contact 10a on fixed terminal 10.
With the electromagnetic relay described above, the limitations of precision inherent in the pressing process result in variations in the thickness of both the sheet used for movable iron member 5 and its plating (on the order of .+-.0.05 mm). These variations adversely affect the distance between surface 5a of movable iron member 5 and movable contact element 4 when member 5 is directly attracted to core 9, and consequently they adversely affect the positional relationship between the surface 5a and movable contact 4a. In other words, imprecision in the thickness of member 5 may lead to variations in the distance between movable contact 4a and fixed contact 10a or in the force of contact between the two. For at least this reason, it is necessary in the prior art to adjust the relay manually in an afterprocess in order to attain the desired operating characteristics.
To ensure that movable contact element 4 and movable iron member 5 are properly isolated from each other, it is necessary to create a specified gap g between the two, as shown ir FIG. 10(b). Thus if the mold used to form the retainer 6 is moved in the direction shown by arrow b--b, it would not be possible to achieve the gap g. It is thus necessary to use a thin sliding core (not pictured) which could move in direction a--a shown in FIG. 10(a). This would make it more complex to construct the molds and, therefore, drive up the cost.
Accordingly, there exists a need for an inexpensive electromagnetic relay with a simple configuration which does not require a sliding core to attain the desired operating characteristics.